The invention relates to an eccentric press.
An eccentric press preamble is known for example from FR-PS No. 1,450,178. This eccentric press comprises a drive mechanism which is provided with a means for continuous adjustment of the working stroke. For this purpose the tool is connected via a lever arrangement to a connecting rod disposed on an eccentric of the drive mechanism. In the articulation joint between lever and connecting rod a support lever engages which guides the joint of the lever arrangement on an adjustable movement path and the foot of which is variable in its position on a circular arc.
To enable the bottom dead center of the ram stroke to be kept constant in the eccentric press of FR-PS No. 1,450,178 the foot of the support lever is guided on a circular arc about the bottom dead center with a radius whose magnitude results from the addition of the lengths of the support lever and of the connecting lever articulated to the ram. A disadvantage here is however that only in the position of the support lever illustrated in FIG. 3 of FR-PS No. 1,450,178 is a ram stroke with the resulting stroke height executed per connecting rod revolution whereas in the positions of the support lever according to FIGS. 4 and 5 in each case two ram strokes per connecting rod revolution are executed, and in the position according to FIG. 4 the stroke heights are equal whereas in the position according to FIG. 5 they are unequal. The reason for this is that as already mentioned the foot of the support lever must be adjusted on the circular arc about the bottom dead center if the latter is to remain unchanged. This in turn means that the position shown in FIG. 3 in which the support lever and the connecting lever articulated to the ram are arranged in elongated position is an extreme position because only in this position of the support lever is a ram stroke with a predetermined stroke height executed per connecting rod revolution. Further, the position shown in FIG. 3 is an extreme position because on an adjustment of the foot of the support lever on the circular arc further to the left in the illustration chosen either a change in the bottom dead center would have to be accepted or if the bottom dead center is maintained a change of length of one of the levers would be necessary. Since however this would certainly not be done because of the high expenditure when operating the press the adjustment path for the support lever and thus the possibility of setting the stroke height is restricted to an adjustment range which in the illustration chosen extends to the right of the instantaneous foot of the support lever in FIG. 3 along the circular arc.
Summarizing, this means that the eccentric press of FR-PS No. 1,450,178 has the disadvantage that a ram stroke with a predetermined height can be executed only in one position of the support lever per connecting rod revolution but there is no position of the support lever which provides a change of the stroke height with only one stroke per connecting rod revolution. On the other hand, it is desirable in eccentric presses to have only one stroke per connecting rod revolution with predetermined adjustable stroke height because only then is it possible per connecting rod revolution to carry out a production operation with the stroke height necessary for a particular production step.